Troubleshooting WordPress re-directs (301)

While trying to configure some internal URL re-writing in nginx for a WordPress site, I ran across an annoying issue:

Regardless of my re-writing efforts, WordPress would issue a re-direct (301) header (?!)

This wouldn’t have been such a big deal if I didn’t want the URL to stay the same in the browser’s address bar. If I didn’t have that requirement, I would naturally have used a simple re-direct.

After spending some time troubleshooting this, and making sure nginx was actually doing what I wanted it to do, I ran across a few posts talking about disabling “canonical redirects” (sic) in WordPress. So adding this snippet to the end of the active theme’s functions.php:

remove_filter('template_redirect','redirect_canonical');

got rid of WordPress re-directs. Unfortunately, another plugin “stepped in” and started doing it instead (this time, it was the Polylang plugin). I’m sure there are a number of other plugins that exhibit this behavior, and it may be possible to circumvent this in many/most/all of them by using something similar to the above snippet, but I still haven’t solved the actual problem.

Using cURL to debug URL re-writing and URL re-direction can save you a lot of time, like this:

curl -I https://yourwebsite.foo

(Please note that the issues I have experienced here are not related to nginx. This would happen in Apache too as the re-directs are issued by the WordPress stack. Once control is handed off to PHP, there’s little the web server can do.)

If you’re playing with nginx, PHP-FPM, and URL re-writing, you may also find this post of interest: URL re-writing with nginx, PHP, and WordPress

URL re-writing with nginx, PHP, and WordPress

There are many posts about nginx, re-directs, PHP, and WordPress. There are somewhat fewer posts that talk about (internal) re-writes, where the request by the web browser is mangled to be served by another resource than the one requested.

For example, I may want a request for https://mysite.foo/cool/penguin to actually be served by https://mysite.foo/coolstuff.php?id=penguin, or simply setup an alias such as https://mysite.foo/cool/penguin to be served by https://mysite.foo/cool/linux, but preserve the URL in the browser address bar.

With PHP-FPM and nginx, you run into an additional problem, which is the fastcgi_parm variables that are passed from nginx to PHP-FPM. So even if you have really fancy URL re-writing configured (and working), the end result may not be passed on to PHP-FPM from nginx.

So solve this, you should look into this construct, which is present in many nginx configurations as a default setup:

fastcgi_param REQUEST_URI $request_uri;

Since your needs probably differ from mine, I wont make this post any longer than it has to be, but that fastcgi_param line above may be a good starting point if you’re experiencing problems with nginx, PHP-FPM, and URL re-writing.

Good luck!